Method for vapor phase catalytic oxidation

ABSTRACT

An object of the present invention is to provide a method for vapor phase catalytic oxidation which is almost free of variations in reaction states in respective reaction tubes of the fixed bed multi-tube heat-exchanger type reactor. 
     Provided is a method for vapor phase catalytic oxidation for obtaining a reaction product gas by using a fixed bed multi-tube heat-exchanger type reactor provided with a plurality of reaction tubes and by feeding a raw material gas inside the reaction tubes packed with a catalyst, wherein the method comprises:
         adjusting pressure losses of the respective reaction tubes so that the pressure losses of the respective reaction tubes after catalyst packing is within ±20% of an average pressure loss of the reaction tubes by: packing an inert substance at a raw material gas inlet portion of the reaction tubes or removing and re-packing the catalyst packed, for a reaction tube having a pressure loss lower than the average pressure loss of the reaction tubes; and removing and re-packing the catalyst packed, for a reaction tube having a pressure loss higher than the average pressure loss of the reaction tubes.

TECHNICAL FIELD

The present invention relates to a method for vapor phase catalyticoxidation involving using a fixed bed multi-tube heat-exchanger typereactor provided with a plurality of reaction tubes and feeding a rawmaterial gas for reaction. The present invention more specificallyrelates to a method for vapor phase catalytic oxidation which is almostfree of variations in reaction states in respective reaction tubes ofthe fixed bed multi-tube heat-exchanger type reactor.

In addition, the present invention relates to a method for packing acatalyst in the reaction tubes used in the method for vapor phasecatalytic oxidation.

BACKGROUND ART

A fixed bed multi-tube heat-exchanger type reactor provided with aplurality of reaction tubes (hereinafter, may be referred to as “fixedbed multi-tube reactor”) has been known up to now. Further, a method ofvapor phase catalytic oxidation using the fixed bed multi-tubeheat-exchanger type reactor has been known.

A method of packing a catalyst in the fixed bed multi-tubeheat-exchanger type reactor generally involves packing by charging thecatalyst from an upper portion of the reactor and allowing the catalystto fall. However, according to this method, packed states differ for therespective reaction tubes because of reasons including: (1) the catalystis powdered or degraded by physical impact of the catalyst charged tofall; and (2) packing time varies. To be specific, a level of powderingor degradation of the catalyst during catalyst packing differs for therespective reaction tubes. Further, long packing time results in a largepacking density, and short packing time results in a small packingdensity. Therefore, according to a conventional packing method, thecatalyst was hardly packed to provide uniform pressure states of therespective reaction tubes, particularly a pressure loss, which becomesan important factor in an oxidation reaction.

No technique exists aiming to provide a uniform pressure loss for therespective reaction tubes of the fixed bed multi-tube reactor, andmethods for solving the problem (1) or (2) are proposed.

Examples of a method of suppressing powdering or degradation of thecatalyst during catalyst packing include the following.

JP 2852712 B discloses a method of improving mechanical strength of acatalyst by coating the catalyst with an organic polymer compound havingdepolymerizing property on a surface of the catalyst. However, a uniformcoating of all of the catalyst is difficult, and catalyst strengthvaries even if the catalyst strength increases as a whole. The coatinghas some effects in reducing the pressure loss, but this method is farfrom a satisfying method of providing a uniform pressure loss for therespective reaction tubes.

Further, JP 05-031351 A discloses a method of interposing a cord-likesubstance, having a shape and a thickness substantially not obstructingfalling of a catalyst, inside a reactor when packing the catalyst froman upper portion of the reactor by allowing to fall. A slight effect isprovided for preventing powdering or degradation of the catalyst, but aneffect of catalyst packing time on packing density is unavoidable. Thus,this method is far from a satisfying method for providing a uniformpressure loss in the respective reaction tubes.

Further, JP 10-277381 A discloses a method involving packing dry iceprior to packing a catalyst by allowing to fall, packing the catalyst,and subsequently vaporizing and removing the dry ice.

Further, JP 09-141084 A discloses a method of packing a catalyst from anupper portion of a reactor involves packing a liquid substance insidethe reactor, subsequently packing the catalyst, and then removing theliquid substance. However, these methods of packing the dry ice or theliquid substance in advance are far from satisfying methods industriallybecause post-treatment after catalyst packing involves time and effort,and handled substances may deteriorate a working environment.

On the other hand, examples of methods of controlling packing operation(time) include the following.

JP 11-333282 A discloses a method using an automatic packing machineprovided with a catalyst feed conveyor and capable of controllingcatalyst packing time. The patent discloses that the packing machineprovides uniform packing time, allowing a uniform pressure loss in therespective reaction tubes. However, a difference in pressure loss mayresult depending on the catalyst, and thus, the method is far fromsatisfying.

Next, a fixed bed multi-tube heat-exchanger type reactor, using aheating medium for absorbing heat of reaction generated inside reactiontubes is conventionally provided with a plate for changing passage ofthe heating medium, called a baffle, to allow uniform flow of theheating medium inside the reactor as much as possible.

Such a fixed bed multi-tube heat-exchanger type reactor provided with abaffle did not have particular problems when a size of a plant wassmall. However, following problems arise when a size of the plant, thatis, a reactor becomes large for increasing productivity as of today.

In other words, a non-uniform portion of a flow of the heating mediumforms inside a reactor shell. A state of poor heat removal forms in partof reaction tubes among a plurality of reaction tubes inside thereactor. A localized abnormal high-temperature zone (hot spot) may formin the reaction tubes which are in a state of poor heat removal,possibly resulting in a reaction out of control.

Further, such different reaction states among the reaction tubes resultin a problem of not preventing formation of reaction tubes in which areaction becomes out of control. In addition, the different statesresult in problems of decreasing an yield of a target product gas and ofdecreasing a catalyst life.

On the other hand, an increase of raw material gas feed for enhancingthe productivity results in portions where heat removal is slower thanheat generation during a reaction, even with a conventional reactor of asmall size. Thus, problems arise such as the above hot spots.

In other words, a conventional method for vapor phase catalyticoxidation using the fixed bed multi-tube heat-exchanger type reactor wasnot a method for vapor phase catalytic oxidation exhibiting satisfactoryresults such as effectively preventing forming of hot spots, yielding alarge amount of a reaction product gas, and having a long catalyst life.

Further, the method of packing the catalyst in the reaction tubes of thefixed bed multi-tube heat-exchanger type reactor as described abovegenerally involves using a packing funnel. The catalyst is packed byproviding the reaction tubes with the packing funnel, and packing thecatalyst by charging the catalyst and allowing the catalyst to fallthrough the packing funnel.

However, the powdered or degraded catalyst formed during transfer,transport, and handling of the catalyst is packed in the reaction tubesas well according to this method. Variations of pressure loss becomeslarge, which is a particularly important factor in an oxidation reactionduring a production step of acrylic acid or methacrylic acid(hereinafter, may be referred to as “(meth)acrylic acid”), and thus,this method is far from a satisfying packing method for providing auniform reaction.

Up to now, no technique is available for separating and removing thepowdered or degraded catalyst in the packed catalyst during catalystpacking. The method as described above is merely proposed forsuppressing powdering or degradation of the catalyst during catalystpacking.

However, those methods had problems in that powdering or degradation ofthe catalyst caused by vibration or impact taking place during transfer,transport, and handling of the catalyst from catalyst production tocatalyst packing or the like in the reaction tubes of the fixed bedmulti-tube reactor were hardly evaded. In addition, the catalyst waspacked in the reaction tubes of the fixed bed multi-tube reactortogether with the powdered or degraded catalyst or the like.

Further, when packing a catalyst in the reaction tubes of the fixed bedmulti-tube heat-exchanger type reactor, the method as described above isemployed to pack the catalyst by allowing the catalyst to fall from anupper portion of the reactor.

However, the catalyst may be powdered or degraded from physical impactduring falling of the catalyst according to this method. For preventingthe above, the catalyst itself must have mechanical strength above somelevel or the packing method must be somehow devised.

The mechanical strength of the catalyst can be improved to a certaindegree by adjusting a molding pressure of the catalyst or devisingoperations of molding or support. However, the catalyst having enhancedmechanical strength through those techniques resulted in reducingspecific surface areas of the catalyst, reducing active sites effectivefor a reaction, and not allowing control of pore distribution effectivefor reaction. Thus, problems arouse such that an yield of the targetproduct was reduced and the catalyst was not practical.

Further, examples of the method of suppressing powdering or degradationof the catalyst during catalyst packing include the above methodsdisclosed in JP 2852712 B, JP 05-031351 A, JP 10-277381 A, and JP09-141084.

However, a uniform coating of all of the catalyst is difficult for themethod of enhancing the mechanical strength of the catalyst by coatingthe catalyst, and catalyst strength varies even if the catalyst strengthincreases as a whole. The coating has some effects in reducing powderingor degradation of the catalyst, but this method requires a step ofcoating during catalyst production and is far from a satisfying method.

The method of interposing a cord-like substance provides an effect ofpreventing powdering or degradation of the catalyst. However, the methodrequires an operation of pulling the cord-like substance upward whilepacking the catalyst. Effects such as extending the packing operationtime or the like are unavoidable, and thus, this method is far fromsatisfying.

The method of packing the dry ice or the liquid substance beforecatalyst packing may result in post treatment taking time and effortafter catalyst packing and deterioration of the working environmentdepending on the handled substances, and thus, is far from satisfyingindustrially.

DISCLOSURE OF THE INVENTION

A first invention of the present invention has been made in view of theabove problems, and an object of the first invention is to provide amethod for vapor phase catalytic oxidation in which a vapor phasecatalytic oxidation reaction through packing a catalyst in reactiontubes of a fixed bed multi-tube heat-exchanger type reactor proceeds inthe respective reaction tubes having a uniform pressure loss at anoptimum temperature in all reaction tubes.

The inventors of the present invention have confirmed during a periodicrepair operation, for example, that some reaction tubes result in cokingin a plant producing acrolein, acrylic acid, or the like through vaporphase catalytic oxidation of propylene using the fixed bed multi-tubeheat-exchanger type reactor. Moreover, the reaction tubes resulting incoking are scattered, and the coking occurs without a pattern in placeswhere cannot be explained by a reaction gas flow or a heating mediumflow inside the reactor.

The inventors of the present invention have studied intensively based onthe fact, and found out that (1) a difference in pressure losses of therespective reaction tubes in the fixed bed multi-tube heat-exchangertype reactor significantly affects conditions of a reaction and (2)pressure loss of the reaction tubes after catalyst packing affects theconditions of a reaction thereafter, to thereby complete the firstinvention of the present invention.

Further, a second invention of the present invention has been made inview of the above problems, and an object of the second invention is toprovide a method for vapor phase catalytic oxidation achievingsatisfactory results such as effectively preventing hot spot formation,yielding a large amount of a reaction product gas, and extending acatalyst life. Those satisfactory results may be obtained by using afixed bed multi-tube heat-exchanger type reactor provided with aplurality of reaction tubes, circulating a heating medium outside thereaction tubes, and feeding a raw material gas inside the reactor packedwith a catalyst.

Examples of methods for preventing the formation of the hot spotsinclude: improvements regarding equipment of the reactor such as areduction of a reaction tube diameter, use of a heating medium having alarge heat capacity, and an increase in amount of the circulatingheating medium for reducing temperature of a catalyst layer inside thereaction tubes; and improvements regarding reaction conditions such aschange in concentration of the raw material gas.

However, similarly and uniformly subjecting all reaction tubes in thereactor with those methods results in high cost and is not preferablealso in terms of improving productivity. Further, reaction states of therespective reaction tubes inside the reactor will not be uniformaccording to those methods.

The inventors of the present invention have studied intensively and haveconfirmed that uniform reaction states of the reactions tubes inside thereactor is effective for allowing effective prevention of hot spotformation, increasing yield of a reaction product gas, and extending acatalyst life. Therefore, the inventors of the present invention havefound out that the method described below provides a method for vaporphase catalytic oxidation achieving the above objects, to therebycomplete the second invention of the present invention.

Further, a third invention of the present invention has been made inview of the above problems, and an object of the third invention is toprovide a method of packing a catalyst or the like in reaction tubes ofa fixed bed multi-tube reactor while separating and removing powdered ordegraded catalyst during catalyst packing when packing a catalyst or thelike in the reaction tubes of the fixed bed multi-tube reactor.

The inventors of the present invention have found out that when packinga catalyst or the like in the reaction tubes of the fixed bed multi-tubereactor, separation and removal of powdered or degraded catalyst or thelike during packing catalyst is important in addition to suppression ofpowdering or degradation of the catalyst or the like during packing, tothereby complete the third invention of the present invention.

Further, a fourth invention of the present invention has been made inview of the above problems, and an object of the fourth invention is toprovide a method of packing a catalyst in reaction tubes of a fixed bedmulti-tube reactor through minimizing powdering or degradation of acatalyst having not so high mechanical strength without affectingcatalyst packing operation time, when packing a catalyst in the reactiontubes of the fixed bed multi-tube reactor.

The inventors of the present invention have conducted various studiesand have found out that when packing a molded catalyst or a supportedcatalyst by allowing the catalyst to fall from an upper portion of thereaction tubes of the fixed bed multi-tube reactor, interposing a chainsubstance in the reaction tubes to reduce a falling rate of the catalystallows suppressing of blocking without affecting the catalyst packingoperation time, and minimizing of powdering or degradation, to therebycomplete the fourth invention of the present invention.

In other words, the first invention of the present invention isdescribed below.

-   -   (1) A method for vapor phase catalytic oxidation for obtaining a        reaction product gas by using a fixed bed multi-tube        heat-exchanger type reactor provided with a plurality of        reaction tubes and by feeding a raw material gas inside the        reaction tubes packed with a catalyst, wherein the method        comprises:

adjusting pressure losses of the respective reaction tubes so that thepressure losses of the respective reaction tubes after catalyst packingis within ±20% of an average pressure loss of the reaction tubes by:packing an inert substance at a raw material gas inlet portion of thereaction tubes or removing and re-packing the catalyst packed, for areaction tube having a pressure loss lower than the average pressureloss of the reaction tubes; and removing and re-packing the catalystpacked, for a reaction tube having a pressure loss higher than theaverage pressure loss of the reaction tubes.

-   -   (2) The method for vapor phase catalytic oxidation according to        the above item (1), wherein the inert substance for adjusting        pressure loss is at least one type of a substance selected from        the group consisting of alumina, silicon carbide, silica,        zirconium oxide, and titanium oxide.    -   (3) The method for vapor phase catalytic oxidation according to        the above item (1) or (2), wherein a shape of the inert        substance for adjusting the pressure loss is spherical,        cylindrical, ring-shaped, or amorphous.    -   (4) The method for vapor phase catalytic oxidation according to        any one of the above items (1) to (3), wherein the catalyst is        an Mo—Bi mixed oxide catalyst or an Mo—V mixed oxide catalyst.    -   (5) The method for vapor phase catalytic oxidation according to        any one of the above items (1) to (4), wherein a shape of the        catalyst is spherical, cylindrical, ring-shaped, or amorphous.    -   (6) The method for vapor phase catalytic oxidation according to        any one of the above items (1) to (5), wherein the catalyst is a        single catalyst or a catalyst diluted with the inert substance.    -   (7) The method for vapor phase catalytic oxidation according to        any one of the above items (1) to (6), wherein the method        further comprises:

predicting reaction states inside the reaction tubes through measurementof catalyst layer temperature of the reaction tubes or through asimulation analysis of a fluid state of a heating medium circulatingoutside the reaction tubes with heat of reaction inside the reactiontubes using a computer; and

determining catalyst packing specifications of the reaction tubesaccording to the prediction results so that nonuniformity of thereaction states among the reaction tubes are reduced for packing thecatalyst in the reaction tubes.

-   -   (8) The method for vapor phase catalytic oxidation according to        the above item (7), wherein items determining the catalyst        packing specifications include items of a catalyst type, a        catalyst amount, a catalyst form, a dilution method for the        catalyst, and lengths of reaction zones.    -   (9) The method for vapor phase catalytic oxidation according to        any one of the above items (1) to (8), wherein the method        further comprises:

packing the catalyst by allowing the catalyst to fall using a funnelwith a net in at least a part of the funnel, for packing the catalyst inthe reaction tubes.

-   -   (10) The method for vapor phase catalytic oxidation according to        any one of the above items (1) to (8), wherein the method        further comprises:

interposing a chain substance inside the reaction tubes so that a lowerend of the chain substance is positioned above an upper end of acatalyst layer; and

packing the catalyst by allowing the catalyst to fall, for packing thecatalyst in the reaction tubes.

-   -   (11) A production method for (meth)acrolein or (meth)acrylic        acid wherein the method comprises:

using the method for vapor phase catalytic oxidation according to anyone of the above items (1) to (10); and

oxidizing propane, propylene, and isobutylene using molecular oxygen toproduce (meth)acrolein or (meth)acrylic acid.

In other words, the second invention of the present invention isdescribed below.

-   -   (12) A method for vapor phase catalytic oxidation for obtaining        a reaction product gas by using a fixed bed multi-tube        heat-exchanger type reactor provided with a plurality of        reaction tubes, circulating a heating medium outside the        reaction tubes, and feeding a raw material gas inside the        reaction tubes packed with a catalyst, wherein the method        comprises:

predicting reaction states inside the reaction tubes; and

changing catalyst packing specifications of the reaction tubes accordingto the prediction results so that nonuniformity of the reaction statesamong the reaction tubes are reduced.

-   -   (13) The method for vapor phase catalytic oxidation according to        the above item (12), wherein the heating medium is for absorbing        heat of reaction generated from the reaction tubes.    -   (14) The method for vapor phase catalytic oxidation according to        the above item (12) or (13), wherein the reaction states inside        the reaction tubes are predicted by grasping thermal states        inside the reaction tubes.    -   (15) The method for vapor phase catalytic oxidation according to        any one of the above items (12) to (14), wherein the thermal        states inside the reaction tubes are grasped by measuring        catalyst layer temperatures of the reaction tubes.    -   (16) The method for vapor phase catalytic oxidation according to        any one of the above items (12) to (14), wherein the thermal        states inside the reaction tubes are grasped through a        simulation analysis using a computer.    -   (17) The method for vapor phase catalytic oxidation according to        the above item (16), wherein a fluid analysis of a heating        medium is conducted through the simulation analysis using a        computer.    -   (18) The method for vapor phase catalytic oxidation according to        the above item (17), wherein the fluid analysis of the heating        medium and an analysis of heat of reaction inside the reaction        tubes are conducted through the simulation analysis using a        computer.    -   (19) The method for vapor phase catalytic oxidation according to        any one of the above items (12) to (18), wherein items        determining the catalyst packing specifications include items of        a catalyst type, a catalyst amount, a catalyst shape, a dilution        method for the catalyst, and lengths of reaction zones.    -   (20) The method for vapor phase catalytic oxidation according to        any one of the above items (12) to (19), wherein the method        further comprises:

stopping feed of the raw material gas to the reaction tubes for a partof the reaction tubes among the plurality of reaction tubes in the fixedbed multi-tube heat-exchanger type reactor.

In other words, the third invention of the present invention isdescribed below.

-   -   (21) A method for packing a catalyst by allowing the catalyst to        fall into reaction tubes of a fixed bed multi-tube reactor using        a funnel, wherein at least a part of the funnel is a net.    -   (22) The method for packing a catalyst according to the above        item (21), wherein the catalyst is a molded catalyst or a        supported catalyst.    -   (23) The method for packing a catalyst according to the above        item (21) or (22), wherein the catalyst is a catalyst for        producing acrylic acid or methacrylic acid.    -   (24) The method for packing a catalyst according to any one of        the above items (21) to (23), wherein a net mesh of the funnel        is smaller than outer diameters of the catalyst and an inert        substance.    -   (25) The method for packing a catalyst according to any one of        the above items (21) to (24), wherein the net of the funnel is        provided at an inclined portion of the funnel and an angle of        the inclination is 10 to 750.

In other words, the fourth invention of the present invention isdescribed below.

-   -   (26) The method for packing a catalyst by allowing the catalyst        to fall into reaction tubes of a fixed bed multi-tube reactor,        wherein the method comprises:    -   interposing a chain substance inside the reaction tubes so that        an lower end of the chain substance is positioned above an upper        end of a catalyst layer; and packing the catalyst in the        reaction tubes of the fixed bed multi-tube reactor.    -   (27) The method for packing a catalyst according to the above        item (26), wherein the catalyst is a molded catalyst or a        supported catalyst.    -   (28) The method for packing a catalyst according to the above        item (26) or (27), wherein the lower end of the chain substance        is positioned 1 to 100 cm above the upper end of the catalyst        layer packed in the reaction tubes.    -   (29) The method for packing a catalyst according to any one of        the above items (26) to (28), wherein the catalyst is a catalyst        for producing acrylic acid or methacrylic acid.    -   (30) The method for packing a catalyst according to any one of        the above items (26) to (29), wherein a size of the reaction        tubes of the fixed bed multi-tube reactor is 2 to 10 m in length        and 50 mm or less in diameter.

Hereinafter, the first invention of the present invention will bedescribed in detail.

The first invention involves a method for vapor phase catalyticoxidation using a fixed bed multi-tube heat-exchanger type reactorprovided with a plurality of reaction tubes.

In other words, a reaction product gas is produced in the reactor bycirculating a heating medium outside the reaction tubes and feeding araw material gas inside the reaction tubes packed with a catalyst.

According to the first invention, the heating medium is preferably usedfor absorbing heat of reaction generated from the reaction tubes. Anymaterial can be used for the heating medium as long as the material hasa function of absorbing the heat of reaction generated from the reactiontubes. Examples of the heating medium include: organic heating mediasuch as partially-hydrogenated triphenyl; and inorganic molten saltssuch as alkali metal (sodium, potassium, or the like) nitrate ornitrite, so-called niter.

Further, according to a method for vapor phase catalytic oxidation ofthe first invention, the raw material gas or the catalyst can beappropriately selected in accordance with a desired type of the reactionproduct gas.

A vapor phase catalytic oxidation reaction of the first invention is amethod widely used for producing (meth)acrolein or (meth)acrylic acidfrom propane, propylene, or isobutylene in the presence of a mixed oxidecatalyst using molecular oxygen or a molecular oxygen-containing gas.

The method generally involves: producing acrylic acid through vaporphase oxidation of propane using an Mo—V—Te mixed oxide catalyst, anMo—V—Sb mixed oxide catalyst, or the like; or producing (meth)acrylicacid by oxidizing propylene or isobutylene in the presence of an Mo—Bimixed oxide catalyst to mainly produce (meth)acrolein in a formerreaction and by oxidizing the (meth)acrolein produced in the formerreaction in the presence of an Mo—V mixed oxide catalyst.

Examples of typical systems of commercialized methods for vapor phasecatalytic oxidation include a one-pass system, an unreacted propylenerecycle system, and a flue gas recycle system. Hereinafter, the systemswill be descried using propylene as an example.

The one-pass system involves: mixing and feeding propylene, air, andsteam from a raw material gas inlet of the respective reaction tubes ofa fixed bed multi-tube reactor for a former reaction; converting the rawmaterial gas to mainly acrolein and acrylic acid; feeding an outlet gasinto the reaction tubes of a fixed bed multi-tube reactor for a latterreaction without separating products from the outlet gas; and oxidizingthe acrolein to acrylic acid. At this time, a general method alsoinvolves feeding air and steam required for a reaction in the latterreaction to the latter reaction in addition to the former reactionoutlet gas.

The unreacted propylene recycle system for recycling a part of theunreacted propylene involves: guiding the reaction product gascontaining acrylic acid obtained from an outlet of the latter reactor toan acrylic acid collecting device; collecting the acrylic acid in anaqueous solution; and feeding a part of waste gas containing theunreacted propylene from the collecting device to the raw material gasinlet of the former reaction.

The flue gas recycle system involves: guiding the reaction product gascontaining acrylic acid obtained from the outlet of the latter reactorto the acrylic acid collecting device; collecting the acrylic acid in anaqueous solution; catalytically combusting and oxidizing all waste gasfrom the collecting device; converting the unreacted propylene or thelike in the waste gas to mainly carbon dioxide and water; and adding apart of the obtained flue gas to the raw material gas inlet of theformer reaction.

The catalyst used in the method for vapor phase catalytic oxidation ofthe first invention is preferably used for packing of the catalyst foracrylic acid formation to the reaction tubes of the fixed multi-tubularreactor used for forming (meth)acrolein or (meth)acrylic acid. Specificexamples of the catalyst include the following.

Examples of the catalyst used for a vapor phase catalytic oxidationreaction for forming (meth)acrylic acid or (meth)acrolein include acatalyst used in the former reaction for converting an olefin intounsaturated aldehyde or unsaturated acid and a catalyst used in thelatter reaction for converting the unsaturated aldehyde into theunsaturated acid. Those catalysts can be employed to either reactionaccording to the first invention.

The following formula (I) represents an example of the catalyst used forthe former reaction.

Mo_(a)W_(b)Bi_(c)Fe_(d)A_(e)B_(f)C_(g)D_(h)E_(i)O_(x)  (I)

(wherein, Mo represents molybdenum; W represents tungsten; Bi representsbismuth; Fe represents iron; A represents at least one type of elementchosen from nickel and cobalt; B represents at least one type of elementselected from the group consisting of sodium, potassium, rubidium,cesium, and thallium; C represents at least one type of element selectedfrom alkali earth metals; D represents at least one type of elementselected from the group consisting of phosphorus, tellurium, antimony,tin, cerium, lead, niobium, manganese, arsenic, boron, and zinc; Erepresents at least one type of element selected from the groupconsisting of silicon, aluminum, titanium, and zirconium; O representsoxygen; a, b, c, d, e, f, g, h, i, and x represent atomic ratios of Mo,W, Bi, Fe, A, B, C, D, E, and O respectively; and if a=12, 0≦b≦10,0≦c≦10 (preferably 0.1≦c≦10), 0≦d≦10 (preferably 0.1≦d≦10), 2≦e≦15,0≦f≦10 (preferably 0.001≦f≦10), 0≦g≦10, 0≦h≦4, and 0≦i≦30; and x is avalue determined from oxidation states of the respective elements.)

The following formula (II) represents an example of the catalyst usedfor the latter reaction of the first invention.

Mo_(a)V_(b)W_(c)Cu_(d)X_(e)Y_(f)O_(g)  (II)

(wherein, Mo represents molybdenum; V represents vanadium; W representstungsten; Cu represents copper; X represents at least one type ofelement selected from the group consisting of Mg, Ca, Sr, and Ba; Yrepresents at least one type of element selected from the groupconsisting of Ti, Zr, Ce, Cr, Mn, Fe, Co, Ni, Zn, Nb, Sn, Sb, Pb, andBi; 0 represents oxygen; a, b, c, d, e, f, and g represent atomic ratiosof Mo, V, W, Cu, X, Y, and O; if a=12, 2≦b≦14, 0≦c≦12, 0≦d≦6, 0≦e≦3, and0≦f≦3; and g is a value determined from oxidation states of therespective elements.)

The above catalysts can be prepared, for example, through a methoddisclosed in JP 63-054942 A.

The reaction tubes used in the method for vapor phase catalyticoxidation of the first invention are packed with the catalyst and, asappropriately, an inert substance for dilution of the catalyst(hereinafter, may be referred to as “diluent”). According to the firstinvention, the catalyst used may be a single catalyst or a catalystdiluted with the inert substance.

Further, packing specifications of the catalyst in the reaction tubesmay be determined comprehensively in view of respective factors such asa catalyst type, a catalyst amount, a catalyst form (shape, size), adilution method for the catalyst (diluent type, diluent amount), andlengths of reaction zones.

The form (shape, size) of the catalyst used in the method for vaporphase catalytic oxidation of the first invention is not particularlylimited, and a molding method for the catalyst is also not particularlylimited. A molded catalyst molded through an extrusion molding method ora tablet compression method can be used, for example. In addition, asupported catalyst structured as a mixed oxide composed of a catalyticcomponent supported on an inert support such as silicon carbide,alumina, zirconium oxide, and titanium oxide may be used.

Further, the shape of the catalyst may be any shape such as spherical,columnar, cylindrical, ring-shaped, star-shaped, and amorphous. Use of aring catalyst, in particular, is effective for preventing thermalstorage in hot spot portions.

Further, any type of the diluent may used as long as it is stable underconditions of a (meth)acrolein and (meth)acrylate oxidation reaction andis not reactive with raw materials such as olefins and products such asunsaturated aldehydes and unsaturated fatty acids. Specific examples ofthe diluent include compounds used for catalyst supports such asalumina, silicon carbide, silica, zirconium oxide, and titanium oxide.Further, a form of the diluent, similar to the catalyst, is not limitedand may be any shape such as spherical, columnar, ring-shaped, a smallpiece, a net, and amorphous. The inert substance is used for adjustingactivity of the whole catalyst in a packed layer to prevent abnormalheat generation during an exothermic reaction.

The amount of the inert substance is suitably determined depending on anexpected catalyst activity. Further, the packing specifications of thecatalyst may differ by layers of reaction zones of one reaction tube.For example, packing specifications of the catalyst packed in an upperportion of a reaction tube may differ from the packing specifications ofthe catalyst packed in a lower portion of the reaction tube. Generally,the number of the reaction zones are preferably set to 2 to 3 within onereaction tube.

Further, a preferable method involves, for example: dividing the packedlayer of the reaction tubes; lowering the catalyst activity andincreasing the amount of the inert substance used to suppress the heatgeneration near the raw material gas inlet; and enhancing the catalystactivity and reducing the amount of the inert substance used toaccelerate the reaction near the raw material gas outlet.

According to the first invention, the fixed bed multi-tubeheat-exchanger type reactor is generally used industrially and is notparticularly limited.

Next, the pressure loss of the reaction tubes in the method for vaporphase catalytic oxidation of the first invention will be described.

The first invention relates to the method for vapor phase catalyticoxidation for producing (meth)acrolein, (meth)acrylic acid, and thelike, in which the pressure losses of the respective reaction tubesafter packing the catalyst in the fixed bed multi-tube heat-exchangertype reactor for a vapor phase oxidation reaction is made uniform. Thefirst invention more specifically relates to the method for vapor phasecatalytic oxidation, characterized in that the pressure losses of therespective reaction tubes after catalyst packing is adjusted within ±20%of an average pressure loss of the reaction tubes by: packing an inertsubstance at the raw material gas inlet portion of the reaction tubes orremoving and re-packing the catalyst packed, for a reaction tube havinga pressure loss lower than the average pressure loss of the reactiontubes; and removing and re-packing the catalyst packed, for a reactiontube having a pressure loss higher than the average pressure loss of thereaction tubes.

Here, the average pressure loss of the reaction tubes is an averagevalue of the pressure loss of 0.5% or more, preferably 1% or more of thereaction tubes randomly selected from the total reaction tubes.

The fixed bed multi-tube reactor used for vapor phase catalyticoxidation of propane, propylene, or the like is provided with severalthousands to several ten thousands of the reaction tubes, and it is verydifficult to uniform packed states of the catalyst in all of thereaction tubes. In other words, catalyst powdering or degradation ishardly made uniform in the respective reaction tubes during catalystpacking. Further, catalyst packing time of the respective reaction tubesis hardly made equal. The packed state of the catalyst, that is thepressure loss, which becomes a particularly important factor in theoxidation reaction, differs greatly by the reaction tubes.

To be specific, a problem caused by the difference in the pressure lossinvolves: changing the amount of gas flowing to the reaction tubes;changing reaction situations by the reaction tubes; and resulting indifferent reaction situations by the reaction tubes even within the samereactor.

The reaction temperature of the reactor is determined according to anaverage value of the reaction states of the total reaction tubes. In theformer reactor for an oxidation reaction of propylene, for example,propylene conversions vary by the reaction tubes. Therefore, thetemperature of the heating medium is determined according to the averagepropylene conversion of the total reaction tubes. Thus, not all reactiontubes are operated under optimum conditions.

In other words, providing a uniform reaction state of the respectivereaction tubes inside the reactor for oxidation reaction, that is thepressure loss, is important for a safe operation of the reactor foroxidation reaction from reasons described below.

-   -   (1) The conversion of the raw material substance reduces and the        yield decreases in a reaction tube with a large amount of gas at        the same reaction temperature. In contrast, an excessive        reaction occurs and side reactions increase to reduce        selectivity, in a reaction tube with a small amount of gas at        the same reaction temperature.    -   (2) Further, excessive side reactions occur in a reaction tube        with a small amount of gas. A reduction of the selectivity        combined with an oxygen shortage in an outlet portion of the        reaction tube causes not only catalyst deterioration, but also        coking.    -   (3) The reaction situations of the respective reaction tubes        differ, so that conditions of the catalyst deterioration differ,        thereby reducing the catalyst life as a whole.

According to the first invention, a method of packing the catalyst tothe reaction tubes of the fixed bed multi-tube heat-exchanger typereactor is not particularly limited. However, the catalyst is preferablypacked while leaving an empty portion in the upper portion of thereaction tubes.

0.5% or more, preferably 1% or more of the reaction tubes are randomlyselected from the total reaction tubes after catalyst packing, and thepressure loss is measured. The pressure loss can be measured by passinga gas of a constant flow rate through the reaction tubes using a massflow meter and measuring the pressure at that time. The gas passedthrough the reaction tubes at the time is not particularly limited, butair is desirably used for safety reasons. The amount of the gas passedthrough the reaction tubes is desirably the amount of the gas actuallypassed through during a reaction at a steady state.

After measuring the pressure losses of the total reaction tubes, theaverage value of the pressure losses of the measured reaction tubes iscalculated. A reaction tube having a pressure loss lower than theaverage value is packed with an inert substance in an empty portion ofthe reaction tube or has the catalyst removed and re-packed, to adjustthe pressure loss within ±20%, preferably +10% of the average value.

A reaction tube having a pressure loss higher than the average value by20% or less has the catalyst removed and re-packed.

If a pressure loss is higher than the average pressure loss of themeasured reaction tubes by 20% or more, the amount of the raw materialgas flowing through the reaction tubes reduces, thereby causing anexcessive reaction. Further, if a pressure loss is lower by 20% or more,the amount of the raw material gas flowing through the reaction tubesincreases, thereby degrading the reactivity.

The respective reaction tubes are generally provided with catalystholders in lower portions, and the catalyst is packed from upperportions of the reaction tubes. The catalyst of the reaction tubes maybe removed by detaching the catalyst holders at the lower portions ofthe reaction tubes and allowing the catalyst to fall. For a mode inwhich a plurality of the reaction tubes shares the catalyst holder, thecatalyst may be removed from the upper portions using a vacuum pump.

Moreover, according to the first invention, the inert substance addedafter measuring the pressure loss for particularly adjusting thepressure loss or the inert substance diluting the catalyst re-packedamong the inert substance packed to the above reaction tubes is referredto as an inert substance for adjustment. The inert substance foradjustment is preferably selected from the group consisting of alumina,silicon carbide, silica, zirconium oxide, and titanium oxide asdescribed above. Further, the form of the inert substance for adjustmentis not particularly limited, and may be any shape such as spherical,columnar, ring-shaped, and amorphous.

Further, according to the first invention, the packing specifications ofthe catalyst may be set considering prediction results of the reactionstates inside the reaction tubes described later.

Uniforming the pressure losses of the respective reaction tubes iseffective for reducing variations of the reaction states by therespective reaction tubes. However, the reaction states mainly concerneffects inside the reaction tubes such as the packed states of thecatalyst in the reaction tubes, but do not concern effects outside thereaction tubes such as a fluid state of the heating medium and a reactorstructure. Therefore, predicting the reaction states inside the reactiontubes considering effects outside the reaction tubes as well and settingthe packing specifications of the catalyst so that the predictedreaction states of the respective reaction tubes become uniform furtherallow reduction in variations of the reaction states by the respectivereaction tubes. The effects outside the reaction tubes include existenceof places having a low heat removal effect depending on the reactiontubes or on positions in the same reaction tube.

Therefore, when packing the catalyst in the reaction tubes or re-packingthe catalyst in the reaction tubes to provide a uniform pressure loss,the reaction states inside the reaction tubes are predicted by measuringthe temperature of the catalyst layers in the reaction tubes orconducting a simulation analysis of the fluid state of the heatingmedium circulating outside the reaction tubes with the heat of reactioninside the reaction tubes using a computer. The packing specificationsof the catalyst in the reaction tubes may be determined according to theprediction results so that nonuniformity of the reaction states amongthe reaction tubes are reduced. A prediction method for the reactionstates inside the respective reaction tubes will be described in detailin the following section regarding the second invention.

Further, according to the first invention, use of a catalyst packingmethod described below for packing the catalyst allows further reductionin variations of the reaction states by respective reaction tubes.

Therefore, when packing the catalyst in the reaction tubes, the catalystmay be packed by being allowed to fall using a funnel having a net in atleast a part thereof. Alternatively, the catalyst may be packed by beingallowed to fall while interposing a chain substance in the reactiontubes so that a lower end of the chain substance is positioned above anupper end of the catalyst layers. The catalyst packing methods will befurther described in detail in the following sections regarding thethird invention and the fourth invention.

Hereinafter, the second invention of the present invention will bedescribed in detail.

The second invention, similar to the first invention, involves a methodfor vapor phase catalytic oxidation using a fixed bed multi-tubeheat-exchanger type reactor provided with a plurality of reaction tubes.

According to the second invention, a description regarding a heatingmedium used is similar to as that regarding the heating medium in thefirst invention.

Further, descriptions regarding a raw material gas and a catalyst aresimilar to those described in the section of the first invention.

Here, specific examples of the catalyst which can be used, similar tothose of the first invention, preferably include the Mo—Bi mixed oxidecatalyst represented by the above formula (1) and the Mo—V mixed oxidecatalyst represented by the above formula (2).

The reaction tubes used in the method for vapor phase catalyticoxidation of the second invention are packed with the catalyst and, asappropriately, an inert substance for diluting the catalyst(hereinafter, may also be referred to as “diluent”).

The packing specifications of the catalyst to the reaction tubes may bedetermined comprehensively in view of respective factors such as acatalyst type, a catalyst amount, a catalyst form (shape, size), adilution method for the catalyst (diluent type, diluent amount), andlengths of reaction zones.

The form (shape, size) of the catalyst used in the method for vaporphase catalytic oxidation of the second invention is similar to thatdescribed in the first invention. A molded catalyst or a supportedcatalyst can be used without any particular limitation, and in addition,a catalyst may be in any shape.

Further, descriptions regarding the diluent type and a mixing ratio ofthe catalyst and the diluent are similar to those described in the firstinvention.

Further, a description that the packing specifications of the catalystmay differ by layers of reaction zones within one reaction tube issimilar to that described in the first invention.

Next, a prediction method for reaction states inside the respectivereaction tubes in the method for vapor phase catalytic oxidation of thesecond invention will be described.

According to the second invention, the reaction states are predicted forpreventing an emergence of reaction tubes in abnormal reaction statessuch as hot spots departing from a normal reaction state.

Therefore, the reaction tubes in abnormal reaction states, differingfrom the normal reaction state or the reaction tubes that may be inabnormal reaction states are predicted.

To be specific, reaction tubes that are not in a uniform state (in areaction state of the same level) with other reaction tubes areselected.

Further, thermal states inside the reaction tubes are preferably graspedfor predicting the reaction states.

Measuring temperature of catalyst layers of the reaction tubes or usinga computer simulation analysis enables grasping the thermal statesinside the reaction tubes.

To be specific, the reaction states different from the reaction statesof other reaction tubes can be predicted: when temperature of a reactiontube is judged higher than that of other reaction tubes from results oftemperature measurements of the catalyst layers of the reactions tubes;and when temperature inside a reaction tube is judged higher than thatinside other reaction tubes from results of computer simulationanalysis.

When grasping the thermal states inside the reaction tubes throughsimulation analysis using a computer, a fluid analysis of the heatingmedium or an analysis combining the fluid analysis of the heating mediumwith an analysis of the heat of reaction inside the reaction tubes, tobe specific, allows grasping of the thermal states.

The fluid analysis of the heating medium includes: determining a layoutof baffles or reaction tubes, a structure of a reactor such as a heatingmedium feed port, and items regarding the heating medium such asphysical properties of the heating medium or a flow through rate of theheating medium; and conducting the simulation. To be specific, aheat-transfer coefficient or a temperature distribution may be computedby calculating a flow direction of the heating medium, a flow rate ofthe heating medium, or the like using a momentum conservation equation,a mass conservation equation, an enthalpy conservation equation, or thelike. According to the second invention, CFX (United Kingdom, CFX Ltd.)can be used for the analysis as a fluid analysis software.

Further, the analysis of the heat of reaction inside the reaction tubesincludes: determining items regarding the reaction tubes such asstructures of the reaction tubes, physical properties of feed gas andthe catalyst, a rate equation, or the like; and conducting thesimulation. To be specific, a reaction level may be determined atrespective minute zones inside the reaction tubes using a momentumconservation equation, a mass conservation equation, an enthalpyconservation equation, a rate equation, or the like. According to thesecond invention, g-PROMS (United Kingdom, AEA Technology plc) can beused for the analysis as an analysis software.

As described above, further incorporating the analysis of the heat ofreaction inside the reaction tubes by considering portions of poor heatremoval using the fluid analysis of the heating medium enablesprediction of the reaction states inside the respective reaction tubesin all places inside the reactor.

The inventors of the present invention have confirmed as a result of thesimulation analysis using a computer in a method for vapor phasecatalytic oxidation using a fixed bed multi-tube heat-exchanger typereactor of a double segment type shown below in FIG. 2 or a fixed bedmulti-tube heat-exchanger type reactor of a ring and doughnut type shownbelow in FIG. 3 that: the heat removal of a flow along the reactiontubes (vertical flow) is worse than that of the flow perpendicular tothe reaction tubes (horizontal flow); and the heat removal of thevertical flow in a central portion of the reactor is much worse thanthat of the vertical flow of an outer peripheral portion of the reactor.

Further, increase of the flow through rate of the heating medium in thefixed bed multi-tube heat-exchanger type reactors was confirmed toimprove the heat removal effect in accordance with the flow through rateof the heating medium of a horizontal flow. However, the increase of theflow through rate of the heating medium did not improve the heat removaleffect in a portion of the heating medium of a vertical flow,particularly in a portion of the heating medium of a vertical flow in acentral portion of the reactor despite the increase.

Further, an existence of a portion of poor heat removal was confirmed ina residence portion of the heating medium in an outer peripheral portionof the reactor according to a method for vapor phase catalytic oxidationusing a fixed bed multi-tube heat-exchanger type reactor of amulti-baffle type of FIG. 4.

Therefore, the portions of poor heat removal are preferably sufficientlyconsidered to carefully predict the reaction states of the reactiontubes in those portions.

Then, according to the second invention, the packing specifications ofthe catalyst in the respective reaction tubes are changed in accordancewith the prediction results based on the above prediction results.

In other words, the packing specifications of the catalyst are changedso that the reaction tubes judged to have different reaction states fromthe other reaction tubes described above are brought into the samereaction states as in the other reaction tubes. That is, the packingspecifications of the catalyst are changed so that nonuniformity of thereaction states is reduced among the reaction tubes.

For example, the packing specifications of the catalyst are changed fora reaction tube judged to have a temperature departing from a givencatalyst layer temperature range, revealed from the temperaturemeasurement of the catalyst layers in the reaction tubes. The packingspecifications are changed so that the reaction tube has a catalystlayer temperature of the same level as those of the other reactiontubes.

Alternatively, as a result of the simulation analysis using a computer,the packing specifications of the catalyst are changed for a reactiontube in a portion of a poor circulating state of the heating medium,which is a reaction tube judged to have a temperature departing from agiven temperature range because of inefficient heat removal of the heatof reaction generated in the reaction tube. The packing specificationsare changed so that the reaction tube has a temperature of the samelevel as the presumed temperature inside other reaction tubes.

A rough standard for the change in the packing specifications will bedescribed below. For example, peak temperatures of the catalyst layersof the respective reaction tubes are determined through the temperaturemeasurement or the simulation. Next, an average value of the peaktemperatures representing a whole reactor is determined based on theresults of the respective peak temperatures. Then, the average value ofthe peak temperatures and the peak temperatures of the respectivereaction tubes are compared. The packing specifications are changed forthe reaction tubes having a temperature difference of 15° C. or more,preferably 10° C. or more, with the average peak temperature. Here, thepeak temperatures of the catalyst layers refer to temperatures ofportions having the highest temperatures when the catalyst is packed inthe reaction tubes in single layers. The peak temperatures of thecatalyst layers refer to temperatures of portions having the highesttemperatures in respective reaction zones when the catalyst is packed inseveral reaction zones. Further, the average peak temperature iscalculated as an average value of the peak temperatures of the reactiontubes disregarding temperatures of portions of remarkably poor heatremoval.

According to the second invention, the packing specifications of thecatalyst can be changed considering the respective factors such as acatalyst type, a catalyst amount, a catalyst form (shape, size), adilution method for the catalyst (diluent type, diluent amount), andlengths of reaction zones. Of those, the packing specifications may bepreferably changed by changing the amounts of the catalyst and thediluent to adjust the mixing ratio of the catalyst and the diluent.

According to the second invention, the packing specifications may bepreferably changed to reduce the temperatures inside the catalyst layersin the reaction tubes, that is, to a direction of suppressing thereaction.

Note that, according to the method for vapor phase catalytic oxidationof the second invention, feeding a large amount of the raw materials forincreasing the productivity may result in places of heat removal slowerthan the increase of the heat of reaction even in places where the heatgeneration and the heat removal were balanced. In such a case, thepacking specifications of the catalyst in the reaction tubes arechanged. In addition, it is effective to stop feed of the raw materialgas to the reaction tubes of extremely poor heat removal portions byplugging or the like to prevent the flow of the gas.

As described above, when setting the packing specifications of thecatalyst according to the first invention, variations of the reactionstates by the respective reaction tubes can be reduced by: predictingthe reaction states inside the reaction tubes according to the secondinvention; and setting the packing specifications of the catalyst in thereaction tubes in accordance with the prediction results so thatnonuniformity of the reaction states among the reaction tubes isreduced.

In other words, the present invention provides, as a more preferablemode of the first invention, a method for vapor phase catalyticoxidation characterized by: predicting the reaction states inside thereaction tubes by measuring the catalyst layer temperature of thereaction tubes or conducting the simulation analysis of the fluid stateof the heating medium circulating outside the reaction tubes and theheat of reaction inside the reaction tubes using a computer; anddetermining the packing specifications of the catalyst in the reactiontubes in accordance with the prediction results so that nonuniformity ofthe reaction states among the reaction tubes is reduced when packing thecatalyst in the reaction tubes according to the first invention. Here,the items determining the packing specifications of the catalyst are asdescribed in the section of the first invention or the second invention.

Hereinafter, the third invention of the present invention will bedescribed in detail.

A catalyst packing method according to the third invention of thepresent invention is a catalyst packing method involving packing of thecatalyst while removing the powdered or degraded catalyst or the likeusing a funnel having a net in at least a part thereof.

A net mesh of the funnel is smaller than the outer diameter of thecatalyst or the like for separating and removing the catalyst or thelike powdered or degraded by vibration or impact during transfer,transport, and handling of the catalyst.

A form, a material, and a size of the funnel are not particularlylimited as long as a part of the funnel consists of a net and the funnelhas a structure not allowing the powdered or degraded catalyst to enterfrom the net portion into the reaction tubes.

An inclined portion of the funnel may be provided with a wire net, apunching metal, or the like for providing a funnel consisting of a netin at least a part thereof.

FIG. 6( a) shows a preferable form of the funnel, and an inclinedportion of a funnel 21 is provided with a net mesh 22. An angle of theinclination is preferably 10 to 75°, more preferably 30 to 500. If theangle of the inclination is 100 or less, the catalyst or the like mayundesirably reside in the funnel or in a wire net portion. If the angleof the inclination is 75° or more, separation of the powdered ordegraded catalyst or the like may undesirably become incomplete becauseof excessive inclination.

The mesh portion is preferably provided to position outside a diameterof the reaction tubes, or a recovery bag (or recovery container) 23 isprovided to cover the mesh portion 22 for preventing the powdered ordegraded catalyst or the like from entering the reaction tubes of thefixed bed multi-tube reactor.

Further, FIGS. 6( b) and (c) respectively are plan views seen from an Adirection and B direction of FIG. 6( a), showing an example of a funnelsize in mm units.

Examples of the funnel material include tinplate, stainless steel, andplastic. The funnel size is suitably selected depending on a size of thereaction tubes of the fixed bed multi-tube reactor.

The funnel may have a general form composed of a conical portion and astraight pipe portion. However, the funnel used is preferably a halffunnel having a perpendicular side and a partially conical side, and adiameter of the straight pipe portion is smaller than an inner diameterof the reaction tubes at least in a portion where the funnel is insertedinto the reaction tubes. Further, the funnel is preferably provided witha wire net on an inclined side of the partial cone and with a powderreservoir for receiving fine powders passing through the net.

The funnel preferably has a size of a sufficient length for separatingor removing the powdered or degraded catalyst or the like using the wirenet provided on the inclined side of the partial cone within a range noteffecting workability.

According to the third invention, the fixed bed multi-tube reactor isgenerally used industrially and is not particularly limited as describedin the sections of the first invention and the second invention.

A description regarding the catalyst used in the third invention issimilar to that in the section of the first invention. Here, specificexamples of the catalyst which can be used, similar to those describedin the first invention, preferably include an Mo—Bi mixed oxide catalystrepresented by the above formula (1) and an Mo—V mixed oxide catalystrepresented by the above formula (2).

According to the third invention, the catalyst used may also be a singlecatalyst or a catalyst diluted with an inert substance, similar to thatin the first invention or the second invention.

The form of the catalyst (shape, size) used in the method for vaporphase catalytic oxidation of the third invention is similar to thatdescribed in the first invention or the like. A molded catalyst or asupported catalyst may be used without any particular limitation.Further, the catalyst may be in any shape.

Further, the descriptions regarding a type and a form of the inertsubstance or an amount of the inert substance used are similar to thosein the first invention.

Further, the packing specifications of the catalyst may differ by layersof reaction zones in one reaction tube as described in the firstinvention.

The catalyst packing method of the third invention more preferablyinvolves purging the reaction tubes with dry air or the like forremoving the powdered product of the catalyst generated inside thereaction tubes. The reaction tubes are packed with the catalyst whileremoving the powdered or degraded catalyst using a funnel with a net inat least a part thereof.

As described above, when packing the catalyst according to the firstinvention, the variations of the reaction states by the respectivereaction tubes can be eliminated by packing the catalyst according tothe packing method of the third invention.

In other words, the present invention, as a more preferable mode of thefirst invention or of a combination of the first invention and thesecond invention, provides a method of packing the catalyst by allowingthe catalyst to fall using a funnel with a net in at least a part of thefunnel when packing the catalyst in the reaction tubes according to thefirst invention.

Hereinafter, the fourth invention of the present invention will bedescribed in detail.

According to the fourth invention, the fixed bed multi-tube reactor isgenerally used industrially and is not particularly limited as describedin the section of the first invention and the second invention. Thefixed bed multi-tube reactor of the fourth invention particularlypreferably has reaction tubes with a length of 2 to 10 m and a diameterof 50 mm or less.

A description regarding the catalyst used in the fourth invention issimilar to that in the section of the first invention. Here, specificexamples of the catalyst which can be used, similar to those describedin the first invention, preferably include an Mo—Bi mixed oxide catalystrepresented by the above formula (1) and an Mo—V mixed oxide catalystrepresented by the above formula (2).

According to the fourth invention, the catalyst used may be a singlecatalyst or a catalyst diluted with an inert substance, similar to thatin the first invention or the second invention.

The form of the catalyst (shape, size) used in the method for vaporphase catalytic oxidation of the fourth invention is similar to thatdescribed in the first invention or the like. A molded catalyst or asupported catalyst may be used without any particular limitation.Further, the catalyst may be in any shape.

Further, the descriptions regarding a type and a form of the inertsubstance or an amount of the inert substance used are similar to thosein the first invention.

The chain substance interposing inside the reaction tubes according tothe fourth invention is not particularly limited as long as thesubstance has a thickness or is a material which reduces a falling speedof the catalyst and does not substantially disturb the falling of thecatalyst. Specific examples of the chain substance include chains ofstainless steel, plastic, or the like and may be a substance which doesnot damage or break from contact with the falling catalyst. Thethickness of the chain substance may be suitably selected from thenumber of the chain substances used and the size of the reaction tubes.

FIG. 8 shows an example of the chain substance having a ring outerdiameter of 6 mm×9 mm used in the present invention. A preferable chainsubstance includes chains composed of an oval ring member having a ringwire diameter of 1 to 1.5 mm and a ring outer diameter of 5 to 15 mm. Awire diameter of less than 1 mm, lacking in strength may result in breakof the chain during use. On the other hand, a wire diameter of more than1.5 mm easily results in winding of the chain to form a “cluster”. Thering outer diameter is preferably within the above range for easyhandling. If a joint exists in the ring member, the joint is preferablywelded.

According to the fourth invention, the number of the chain substancesused for interposing inside the reaction tubes is at least one. Thelarger the number, the larger the effect is for suppressing thepowdering or the degradation of the catalyst during catalyst packing.However, an excess number may hinder the catalyst from falling, andthus, the number may be suitably selected from the thickness of thechain substance, the size of the reaction tubes, or the like.

The length of chain substance may be provided so that a lower end of thechain substance is positioned 1 to 100 cm, preferably 1 to 50 cm, andmore preferably 5 to 20 cm above an upper end of a catalyst layer packedin the reaction tubes.

According to the fourth invention, the packing specifications of thecatalyst are not particularly limited. However, multi-layer packing ispreferable for changing activity of the catalyst packed inside thereaction tubes to increase reaction efficiency of a target reactionusing the reaction tubes packed with the catalyst.

The multi-layer packing provides several catalyst layers by dividing thepacked layers of the reaction tubes to change the activity of thecatalyst packed inside the reaction tubes. In such a case, the catalystis preferably packed inside the reaction tubes by preparing a chainsubstance with an adjusted length for each of the catalyst layers andchanging to an adequate chain substance when packing the target catalystlayer.

An interposing means for the chain substance inside the reaction tubesincludes a method of hanging the chain substance on a packing funnelprovided on an upper portion of the reaction tubes. A specific exampleof the method, as shown in FIGS. 7( a) to (c), involves: welding in across a stainless steel linear member 32 to a stainless steel (SUS304,for example) ring 31 having a larger diameter than that of a reactiontube so that the chain substance does not fall inside the reaction tube;and fixing a chain 33 to the cross portion using a stainless steel wire.

As described above, when packing the catalyst according to the firstinvention, the variations of the reaction states by the respectivereaction tubes can be eliminated by packing the catalyst according tothe packing method of the fourth invention.

In other words, the present invention, as a more preferable mode of thefirst invention or of a combination of the first invention and thesecond invention, provides a method of packing the catalyst by allowingthe catalyst to fall by interposing the chain substance inside thereaction tubes so that the lower end of the chain substance ispositioned above the upper end of the catalyst layer when packing thecatalyst in the reaction tubes according to the first invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a mode of a fixed bed multi-tube heat-exchangertype reactor used in the present invention.

FIG. 2 is a diagram of a mode of a fixed bed multi-tube heat-exchangertype reactor used in the present invention.

FIG. 3 is a diagram of a mode of a fixed bed multi-tube heat-exchangertype reactor used in the present invention.

FIG. 4 is a diagram of a mode of a fixed bed multi-tube heat-exchangertype reactor used in the present invention.

FIG. 5 is a diagram for explaining Example 6 of the present invention.

FIG. 6( a) is a perspective view showing an embodiment mode of a funnelused in a catalyst packing method of the present invention.

FIG. 6( b) is a plan view of (a) seen from an A direction.

FIG. 6( c) is a plan view of (a) seen from a B direction.

FIG. 7( a) is a perspective view showing an embodiment mode of a chainsubstance used in a catalyst packing method of the present invention.

FIG. 7( b) is a plan view of (a) seen from an A direction.

FIG. 7( c) is a plan view of (a) seen from a B direction.

FIG. 8 is an enlarged view showing an embodiment mode of a chainsubstance used in a catalyst packing method of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be further described in detailby way of examples and comparative examples, but the present inventionis not limited by the examples so long as not departing from the scopeof the invention.

<First Invention> <Standard Conditions>

Reaction Tubes of a Fixed Bed Multi-Tube Heat-Exchanger Type Reactor

A pilot device of a fixed bed reactor consists of a reaction tube whichhas an inner diameter of 27 mm and a length of 5 m and is provided witha jacket for a heating medium. The pilot device can uniformly controltemperature using niter as the heating medium.

Former Reaction Catalyst (Propylene Vapor Phase Catalytic OxidationCatalyst)

A catalyst of the following composition (atomic ratio) was prepared by amethod disclosed in JP 63-054942 A as the propylene vapor phasecatalytic oxidation catalyst.

Mo:Bi:Co:Fe:Na:B:K:Si:O=12:1:0.6:7:0.1:0.2:0.1:18:X

Wherein, X is a value determined from oxidation states of respectivemetal elements.

The reaction tube was packed with 0.86 L of the catalyst, 0.43 L of amixture containing 70% of the catalyst and 30% of alumina balls involume ratio thereon, and 0.43 L of a mixture containing 50% of thecatalyst and 50% of the alumina balls in volume ratio further thereon.

Former Reaction Conditions

A raw material gas having a composition of 9.5 mol % of propylene, 71.9mol % of air, and 18.6 mol % of steam was fed to the reaction tube ofthe fixed bed multi-tube reactor of the pilot device or an actualequipment at a flow rate of 1,032 NL/H.

Reaction Pressure

An outlet pressure of a latter reactor was adjusted to 50 KPaG (gaugepressure).

EXAMPLE 1

A pressure loss of the reaction tube when feeding air of the same volume(1,032 NL/H) as the volume of gas fed under the standard reactionconditions was 7.1 KPa after packing the former catalyst in the reactiontube of the pilot device under standard conditions.

Further, reaction performance of the reaction tube at a reactiontemperature of 323° C. resulted in propylene conversion of 98.0% andtotal yield of acrylic acid and acrolein of 92.1%. (Here, the reactiontemperature can also be referred to as “heating medium temperature”because the reaction temperature can be determined from the temperatureof the heating medium circulating outside the reaction tube forabsorbing heat of reaction generated from the reaction tube.)

COMPARATIVE EXAMPLE 1

The catalyst was packed following the same method as in Example 1 exceptthat catalyst packing time was changed. As a result, the pressure lossof the reaction tube after catalyst packing was 5.6 KPa, and the volumeof air increased to reach the same pressure loss of 7.1 KPa as inExample 1 was 1,200 NL/H.

The reaction was conducted at a heating medium temperature of 323° C.following the same method as in Example 1 except that the gas volume fedto the former reaction tube was changed to 1,200 NL/H. The propyleneconvention was 96.7% and the total yield of the acrylic acid and theacrolein was 90.1%, resulting in a very low conversion compared toExample 1.

COMPARATIVE EXAMPLE 2

The catalyst was packed following the same method as in Example 1 exceptthat catalyst packing time was changed. As a result, the pressure lossof the reaction tube after catalyst packing was 8.4 KPa, and the volumeof air decreased to reach the same pressure loss of 7.1 KPa as inExample 1 was 920 NL/H.

The reaction was conducted at a heating medium temperature of 323° C.following the same method as in Example 1 except that the gas volume fedto the former reaction tube was changed to 920 NL/H. The propyleneconversion was 98.8% and the total yield of the acrylic acid and theacrolein was 91.6%, resulting in an excessive oxidation reaction.

EXAMPLE 2

Alumina balls as an inert substance were packed into the reaction tubeof Comparative Example 1, so that the pressure loss of the reaction tubewas 7.1 KPa, the same as in Example 1, when feeding air of the samevolume (1,032 NL/H) as the volume of gas fed under the standard reactionconditions. The gas volume fed to the former reactor was 1,302 NL/H, andthe reaction was conducted under the same conditions as in Example 1 ata heating medium temperature of 323° C. As a result, the propyleneconversion was 97.9% and the total yield of the acrylic acid and theacrolein was 92.0%, substantially the same result as in Example 1.

Table 1 collectively shows results of Examples 1 and 2 and ComparativeExamples 1 and 2.

TABLE 1 With or without Pressure correction of Total loss catalyst Reac-Pro- yield of after packing tion pylene acrolein catalyst specificationtemper- conver- and packing for adjusting ature sion acrylic (KPa)pressure loss (° C.) (%) acid (%) Example 1 7.1 Without 323 98.0 92.1correction Comparative 5.6 Without 323 96.7 90.1 Example 1 correctionComparative 8.4 Without 323 98.8 91.6 Example 2 correction Example 2 5.6With correction 323 97.9 92.0

EXAMPLES 3 to 5 and COMPARATIVE EXAMPLES 3 and 4

Effects of the pressure loss on the catalyst over time after catalystpacking were determined using the actual equipment.

The actual equipment was a fixed bed multi-tube exchanger reactor having15,000 reaction tubes. The reaction conditions were basically the sameas in Example 1, and an average volume of the gas fed per reaction tubewas 1,250 NL/H.

8 reaction tubes packed with a catalyst in different packed states wereprepared by changing the catalyst packing time and the catalyst packingmethod, for Examples 3 to 5 and Comparative Examples 3 and 4,respectively.

Table 2 shows the pressure loss of the reaction tubes after catalystpacking and the pressure loss 1 year after start of the operation.Further, the pressure losses of the 150 reaction tubes of the reactorwere measured. The results showed that an average pressure loss was 8.5KPa, the same value as the pressure loss of the reaction tube in Example3.

Table 2 also shows the pressure loss of the reaction tubes aftercatalyst packing and the pressure loss 1 year after the start of theoperation in Examples 4 and 5 and Comparative Examples 3 and 4.

The volume of gas flowing through the reaction tubes having a pressureloss higher than the average pressure loss was smaller than the volumeof the gas flowing in the reaction tubes having the average pressureloss. As a result, an excessive reaction occurred, not only causingcatalyst deterioration, but also becoming a cause of coking. InComparative Example 3 and Comparative Example 4, outlet portions of thereaction tubes were black, causing coking, and completely blocked. Inother words, the reaction tubes were causing yield reduction at thebeginning of coking and were completely clogged ultimately, to result inthe reaction tubes not being used effectively for the oxidationreaction.

TABLE 2 With or without Pressure correction of loss catalyst Pressureafter packing Difference loss after catalyst specification with average1 year packing for adjusting pressure operation (KPa) pressure loss loss(%) (KPa) Example 3 8.5 Without 0 8.6 correction Example 4 9.4 Without+10 9.8 correction Example 5 10.2 Without +20 11.2  correctionComparative 11.1 Without +30 Not Example 3 correction measurableComparative 10.6 Without +24 Not Example 4 correction measurable

<Second Invention>

FIG. 1 shows a first embodiment mode of the fixed bed multi-tubeheat-exchanger type reactor used in a method for vapor phase catalyticoxidation of the second invention.

FIG. 1 shows: a reactor 1; a raw material gas introducing port (for adownflow case) or a reaction product gas discharging port (for an upflowcase) 2; a reaction product gas discharging port (for a downflow case)or a raw material gas introducing port (for an upflow case) 3; areaction tube (catalyst packed inside) 4; an upper tube plate 5; a lowertube plate 6; baffles 7, 8, and 9; a heating medium outlet nozzle 10; aheating medium inlet nozzle 11; a heating medium inlet line for reactiontemperature adjustment 13; and a heating medium overflow line 14.

Note that the fixed bed multi-tube heat-exchanger type reactor in FIG. 1has a for case of structure passing the heating medium in an upflowdirection, but the heating medium can be obviously passed in a downflowdirection as well according to the present invention.

The raw material gas is mixed with air and/or a diluent gas, a recyclegas, or the like, introduced from the raw material gas introducing port(2 or 3) to the reactor (1), and fed to the reaction tube (4) where thecatalyst is packed. The reaction product gas produced by oxidationthrough a catalytic oxidation reaction inside the reaction tube or anunreacted gas is discharged from the reaction product gas dischargingport (3 or 2).

The heating medium is introduced from the heating medium inlet nozzle(11) to a reactor shell by a pump (12), passed through inside thereactor shell while removing the heat of reaction generated inside thereaction tube, discharged from the heating medium outlet nozzle (10),and circulated by the pump. Temperature of the heating medium iscontrolled by introducing a cooling medium from a cooling medium nozzle(13), and the medium introduced from the nozzle (13) is discharged fromthe heating medium overflow line (14).

A structure of the baffles of the fixed bed multi-tube heat-exchangertype reactor according to the present invention is not particularlylimited. Any type of the fixed bed multi-tube heat-exchanger typereactor can be used including a double segment baffle type as shown inFIG. 2, a ring and doughnut baffle type as shown in FIG. 3, and a multibaffle type as shown in FIG. 4, for example. In FIGS. 2 to 4, shapes ofthe baffles and flow of the heating medium are described.

REFERENCE EXAMPLE 1

The following experiment indicates that the reaction tube located in aportion of poor heat removal can be brought under the same reactionconditions as other reaction tubes by changing the packingspecifications of the catalyst.

The fixed bed multi-tube heat-exchanger type reactor consisting of astainless steel reaction tube having an inner diameter of 27 mm and alength of 5 m was used. Partially hydrogenated triphenyl, which is anorganic heating medium, was used as a heating medium. The fixed bedmulti-tube heat-exchanger type reactor is of a type capable ofcirculating the heating medium by an external pump and controlling thevolume of the heating medium circulating.

The reaction tube was packed with a mixture containing 80% of an Mo—V—Sbcatalyst prepared following a conventional procedure and 20% of aluminaballs in volume ratio to a height of 1.8 m and a mixture containing 50%of the catalyst and 50% of the alumina balls in volume ratio to a heightof 1.0 m thereon.

A mixed gas consisting of 6 mol % of acrolein, 7 mol % of oxygen, 16 mol% of steam, nitrogen, or the like were fed to the fixed bed multi-tubeheat-exchanger type reactor under a condition of a contact time of 2seconds at a heating medium temperature of 265° C. with the heatingmedium circulating at 2.5 m³/h.

An acrolein conversion, an acrylic acid yield, and a peak temperature ofthe catalyst layer at this time were respectively 99%, 97%, and 295° C.

Here, the acrolein conversion and the acrylic acid yield wererespectively determined as follows.

Acrolein conversion (mol %)={(moles of acrolein reacted)/(moles ofacrolein fed)}×100

Acrylic acid yield (mol %)={(moles of acrylic acid produced)/(moles ofacrolein fed)}×100

Further, the peak temperature of the catalyst layer was determined byinserting a multi-point thermocouple (20 points) to the reaction tubeand measuring the temperatures of the respective points of measurement.

Next, an experiment was conducted following the same method as describedexcept that the volume of the heating medium circulating was changed to0.5 m³/h. As a result, the acrolein conversion, the acrylic acid yield,and the peak temperature of the catalyst layer were respectively 99.7%,95.5%, and 313° C.

Next, an experiment was conducted following the same method as describedabove with the volume of the heating medium circulating remained at 0.5m³/h except that the packing specifications of the catalyst in thereaction tube was changed. Here, the Mo—V—Sb catalyst was packed to aheight of 1.3 m, and a mixture containing 40% of the catalyst and 60% ofthe alumina balls in volume ratio was packed thereon to a height of 1.5m. As a result, the acrolein conversion, the acrylic acid yield, and thepeak temperature of the catalyst layer were respectively 99.1%, 97%, and296° C. The results were similar to the results of the initialexperiment circulating the heating medium at 2.5 m³/h.

The above results confirmed that a conversion, an yield, and a peaktemperature similar to those obtained in good circulating states of theheating medium (volume of the heating medium circulated at 2.5 m³/h) canbe attained by changing the catalyst packing specifications in cases ofpoor circulating states of the heating medium (volume of the heatingmedium circulated at 0.5 m³/h as described above).

EXAMPLE 6

The multi-point thermocouples were provided for measuring the catalystlayer temperatures of the reaction tubes at positions (A to H) shown inFIG. 5 using the fixed bed multi-tube heat-exchanger type reactorconsisting of 20,000 stainless steel reaction tubes having an innerdiameter of 27 mm and a length of 3 m. The reactor shell was providedwith double segment type baffles for changing a flow path of the heatingmedium. The partially hydrogenated triphenyl was used as the heatingmedium.

All of the reaction tubes were packed with a mixture containing 80% ofthe Mo—V—Sb catalyst, which is the same catalyst as in Example 1, and20% of alumina balls in volume ratio to a height of 1.8 m and a mixturecontaining 50% of the catalyst and 50% of the alumina balls in volumeratio to a height of 1.0 m thereon. The alumina balls were furtherpacked thereon to upper portions of the reaction tubes.

A mixed gas consisting of 6 mol % of acrolein, 7 mol % of oxygen, 16 mol% of steam, and the remaining composed of mostly nitrogen and minuteacrylic acid, acetic acid, carbon dioxide, carbon monoxide, or the likewas fed to the fixed bed multi-tube heat-exchanger type reactor under acondition of a contact time of 2.5 seconds. The temperature of theheating medium at this time was 260° C.

Table 3 shows the peak temperatures of the catalyst layer inside therespective reaction tubes positioned at A to H.

TABLE 3 Difference with the Reaction tube Catalyst layer peak averagepeak position temperature (° C.) temperature (° C.) A 290 — B 291 — C290 — D 291 — E 291 — F 308 17 G 310 19 H 315 24 The average peaktemperature is 291° C., an average value of A to E.

From the results of Table 3, the average peak temperature in this casewas defined as 291° C.

The acrolein conversion and the acrylic acid yield at this time wererespectively 99.2% and 95.3%.

Next, the catalyst layer peak temperatures of the respective reactiontubes inside the reactor and the average peak temperature were compared.The reaction tubes having a temperature difference of more than 10° C.(the reaction tubes positioned at F, G, and H) were plugged or thepacking specifications of the catalyst were changed therefor.

Area 1 described in FIG. 5 was a portion of the poorest heat removal.Therefore, tops and bottoms of the reaction tubes positioned in Area Aincluding H were plugged so that a reactant gas did not flow.

The packing specifications of the reaction tubes positioned in Area 2including F and G described in FIG. 5 were changed as follows. A mixturecontaining 90% of the catalyst and 10% of the alumina balls in volumeratio was packed to a height of 1.3 m, and a mixture containing 40% ofthe catalyst and 60% of the alumina balls in volume ratio was packedthereon to a height of 1.0 m. The alumina balls were further packedthereon to the upper portions of the reaction tubes.

The reaction tubes positioned in Area 3 including A, B, C, D, and Edescribed in FIG. 5 had the catalyst layer peak temperatures comparableto the average peak temperature. Thus, the packing specifications werenot changed.

The raw material gas was fed to the reaction tubes of the abovespecifications under the similar conditions as described above. That is,a mixed gas consisting of 6 mol % of acrolein, 7 mol % of oxygen, 16 mol% of steam, the remaining composed of mostly nitrogen and minute acrylicacid, acetic acid, carbon dioxide, carbon monoxide, or the like was fedto the fixed bed multi-tube heat-exchanger type reactor under acondition of a contact time of 2.5 seconds. The temperature of theheating medium at this time was 262° C.

Table 4 shows the peak temperatures of the catalyst layer inside therespective reaction tubes positioned at A to H.

TABLE 4 Difference with the Reaction tube Catalyst layer peak averagepeak position temperature (° C.) temperature (° C.) A 291 — B 292 — C290 — D 291 — E 292 — F 293 2 G 292 1 H — — The average peak temperatureis 291° C., an average value of A to E.

From the results of Table 4, the average peak temperature in this casewas defined as 291° C. The results confirmed that the respectivereaction tubes had the catalyst layer peak temperatures comparable tothe average peak temperature.

The acrolein conversion and the acrylic acid yield at this time wererespectively 99.1% and 96.8%.

As described above, the packing specifications of the catalyst layers inthe reaction tubes were changed to be in similar reaction states in thesame reactor. As a result, nonuniformity of the reaction states wasreduced among the respective reaction tubes, and the reaction states ofthe respective reaction tubes inside the reactor could be made uniform.

From the above, a method for vapor phase catalytic oxidation exhibitingsatisfactory results such as effectively preventing formation of hotspots, having high yield of the reaction product gas, and having a longcatalyst life could be provided.

<Third Invention>

The catalyst for packing used in the following Examples 7 to 9 was anMo—Bi catalysts molded into cylinders having an outer diameter of 6 mm,an inner diameter of 2 mm, and a height of 6 mm through tabletcompression. Spherical mullite balls having an outer diameter of 6 mmwere used as an inert substance for dilution (diluent).

According to the third invention, powdering and degradation are definedas follow:

1) powder ratio: a ratio of powder passed through a screen of 10 meshwith respect to the total normal catalyst; and2) crack ratio: a ratio of cracked catalyst with respect to the totalnormal catalyst

EXAMPLE 7

The catalyst was packed in the reaction tube of the fixed bed multi-tubereactor using a packing funnel with a wire net shown in FIG. 6. Thepacking funnel had a net mesh of 3 mm and an angle of inclination of thewire net portion of 35°. A polyethylene bucket was set at a lowerportion of the packing funnel. 580 g of the Mo—Bi catalyst, as a singlecatalyst, was allowed to fall from the end of the packing funnel in 60seconds. The powder ratio and the crack ratio of the catalyst separatedbelow the wire net at this time were respectively 0.51% and 1.04%, and arecovery rate of the powdered or degraded catalyst was substantially100%.

The recovery rate of the powdered or degraded catalyst was obtained byremoving the packed catalyst without powdering or degrading and wasrepresented as a ratio with respect to the total catalyst removedfollowing the definitions of the 1) powder ratio and the 2) crack ratio.

EXAMPLE 8

580 g of the Mo—Bi catalyst, as a single catalyst, was allowed to fallfrom the end of the packing funnel in 60 seconds under same conditionsas in Example 7 except that the angle of the inclination of the wire netportion of the packing funnel was changed to 50°. The powder ratio andthe crack ratio of the catalyst separated below the wire net at thistime were respectively 0.6% and 0.84%, and recovery and separation rateof the catalyst at the wire net was about 90%.

EXAMPLE 9

The catalyst was packed in the reaction tube of the fixed bed multi-tubereactor using a packing funnel with a wire net shown in FIG. 6. Thepacking funnel had a wire net mesh of 4 mm and an angle of inclinationof the wire net portion of 45°. A polyethylene bucket was set at a lowerportion of the packing funnel. 175 g of the Mo—Bi catalyst and 220 g ofa diluent were allowed to fall from the end of the packing funnel in 40seconds. The powder ratio and the crack ratio of the catalyst separatedbelow the wire net at this time were respectively 0.51% and 1.29%, andrecovery rate of the powdered or degraded catalyst was 95%.

<Fourth Invention>

Hereinafter, the catalysts for packing used in Examples 10 to 13 wereprepared as follows.

94.1 g of ammonium paramolybdate was dissolved in 400 ml of pure waterby heating. Next, 7.18 g of ferric nitrate, 25.8 g of cobalt nitrate,and 38.7 g of nickel nitrate were dissolved in 60 ml of pure water bywarming. The two liquid mixtures were gradually mixed with sufficientstirring.

Next, to the mixed liquid (slurry), a liquid mixture containing 0.85 gof borax, 0.38 g of sodium nitrate, and 0.36 g of potassium nitratedissolved in 40 ml of pure water by warming was added and sufficientlystirred. Then, 57.8 g of bismuth subcarbonate and 64 g of silica wereadded to the slurry for mixing under stirring. The slurry was subjectedto drying by heating, and then to heat treatment in air at 300° C. for 1hour. The obtained solid was molded into cylinders having an outerdiameter of 6 mm, an inner diameter of 2 mm, and a height of 6 mmthrough table compression using a compact molding device. The cylinderswere calcined in a muffle furnace at 480° C. for 8 hours, to therebyobtain a catalyst. The obtained catalyst is a mixed oxide having thefollowing atomic ratio, which is a composition ratio of metal componentsof the catalyst calculated from the raw materials.

Mo:Bi:Co:Ni:Fe:Na:B:K:Si=12:5:2:3:0.4:0.2:0.2:0.08:24

The obtained catalyst was an Mo—Bi catalyst molded into cylinders havingan outer diameter of 6 mm, an inner diameter of 2 mm, and a height of 6mm through tablet compression. Spherical mullite balls having an outerdiameter of 6 mm were used as an inert substance for dilution (diluent).

According to the fourth invention, powdering and degradation are definedas follows:

1) powder ratio: a ratio of powder passed through a screen of 14 meshwith respect to the total normal catalyst; and2) crack ratio: a ratio of cracked catalyst with respect to the totalnormal catalyst.

EXAMPLE 10

A stainless steel spring was fixed at a bottom portion of a stainlesssteel straight pipe having an inner diameter of 26.6 mm and a pipelength of 4.4 m at a position 50 mm above the bottom portion of thestraight pipe. A stainless steel chain having a length of 2.65 m andconsisting of an oval ring member having a wire diameter of 1.5 mm andan outer diameter of 6 mm×9 mm was hanged (free fall distance of 1.7 m)from an upper portion of a reaction tube. 650 g of the Mo—Bi catalyst asa single catalyst was packed by allowing the catalyst to fall from theupper portion. Note that a distance between a lower end of the chain andan upper end of the catalyst layer was 5 cm. The powder ratio and thecrack ratio at this time were respectively 0.2% and 3.1%.

COMPARATIVE EXAMPLE 5

650 g of the Mo—Bi catalyst as a single catalyst was packed by allowingthe catalyst to fall as in Example 10 except that a chain was not used(free fall distance of 4.35 m). The powder ratio and the crack ratio atthis time were respectively 0.9% and 25.0%.

EXAMPLE 11

A stainless steel spring was fixed in the reaction tube of the Example10 at a position 1.55 m above the bottom portion of the reaction tube. Achain having a length of 1.85 m was hanged (free fall distance of 1.0 m)from the upper portion of the reaction tube. A diluent catalystcontaining 195 g of the Mo—Bi catalyst and 240 g of the diluent mixedwas packed by allowing the catalyst to fall from the upper portion. Notethat a distance between the lower end of the chain and the upper end ofthe catalyst layer was 5 cm. The powder ratio and the crack ratio atthis time were respectively 0.4% and 4.8%.

COMPARATIVE EXAMPLE 6

The diluent catalyst in Example 11 was packed by allowing the catalystto fall as in Example 11 except that a chain was not inserted (free falldistance of 2.85 m). The powder ratio and the crack ratio at this timewere respectively 0.9% and 19.4%.

EXAMPLE 12

A stainless steel spring was fixed in the reaction tube of the Example10 at a position 2.55 m above the bottom portion of the reaction tube. Achain having a length of 0.9 m was hanged (free fall distance of 0.95 m)from the upper portion of the reaction tube. A diluent catalystcontaining 140 g of the Mo—Bi catalyst and 345 g of the diluent mixedwas packed by allowing the catalyst to fall from the upper portion. Notethat a distance between the lower end of the chain and the upper end ofthe catalyst layer was 50 cm. The powder ratio and the crack ratio atthis time were respectively 0.3% and 5.6%.

COMPARATIVE EXAMPLE 7

The diluent catalyst in Example 12 was packed by allowing the catalystto fall as in Example 12 except that a chain was not inserted (free falldistance of 1.85 m). The powder ratio and the crack ratio at this timewere respectively 0.6% and 13.4%.

EXAMPLE 13

A stainless steel spring was fixed at a bottom portion of apolycarbonate straight pipe having an inner diameter of 24.0 mm and apipe length of 1.0 m. A chain having a length of 0.7 m was hanged (freefall distance of 0.3 m) from the upper portion of the reaction tube. 35g of the Mo—Bi catalyst as a single catalyst was packed by allowing thecatalyst to fall. Note that a distance between the lower end of thechain and the upper end of the catalyst layer was 2 cm. The powder ratioand the crack ratio at this time were respectively 0.3% and 0.9%.

COMPARATIVE EXAMPLE 8

35 g of the Mo—Bi catalyst as a single catalyst was packed by allowingthe catalyst to fall as in Example 13 except that a chain was notinserted (free fall distance of 1.0 m). The powder ratio and the crackratio at this time were respectively 0.3% and 3.0%.

INDUSTRIAL APPLICABILITY

According to the first invention of the present invention, in a methodfor producing acrolein and acrylic acid, and the like from a rawmaterial gas such as propane and propylene through vapor phase catalyticoxidation with molecular oxygen or a molecular oxygen-containing gasusing a fixed bed multi-tube heat-exchanger type reactor, not only arethe variations of the reaction states among the respective reactiontubes suppressed and is the improvement on catalyst life achieved, butalso acrolein, acrylic acid, and the like can be produced in highyields. Such results can be obtained by packing the catalyst in therespective reaction tubes of the fixed bed multi-tube heat-exchangertype reactor and then using the reactor for reaction after adjusting thepressure loss of the reaction tubes to be uniform.

Further, according to the second invention of the present invention, amethod for vapor phase catalytic oxidation achieving satisfactoryresults such as effectively preventing hot spot formation, yielding alarge volume of the reaction product gas, and extending catalyst lifecan be provided. These satisfactory results may be obtained by using thefixed bed multi-tube heat-exchanger type reactor provided with aplurality of reaction tubes, circulating a heating medium outside thereaction tubes, and feeding the raw material gas inside the reactiontubes packed with the catalyst.

Further, according to the third invention of the present invention, theuse of the funnel with a net in at least a part of the funnel forpacking the catalyst in the reaction tubes of the fixed bed multi-tubereactor allows substantially complete separation or removal of thepowdered or degraded catalyst generated during transfer, transport, andhandling of the catalyst. Therefore, mechanical strength of the catalystdoes not have to be increased more than necessary concerning powderingor the like of the catalyst during packing thereof. Limitations oncatalyst design become small, enabling catalyst preparation under abroad range of conditions.

According to the fourth invention of the present invention, theresistance of the chain substance can remarkably reduce powdering ordegradation of the catalyst caused by physical impact during falling ofthe catalyst, when packing the catalyst in the fixed bed multi-tubereactor. Therefore, mechanical strength of the catalyst does not have tobe increased more than necessary concerning powdering or the like of thecatalyst during packing thereof. Limitations on catalyst design becomesmall, enabling catalyst preparation under a broad range of conditions.Further, blocking can be prevented during catalyst packing.

1-20. (canceled)
 21. A method for packing a catalyst by allowing thecatalyst to fall into reaction tubes of a fixed bed multi-tube reactorusing a funnel, wherein at least a part of the funnel is a net.
 22. Themethod for packing a catalyst according to claim 21, wherein thecatalyst is a molded catalyst or a supported catalyst.
 23. The methodfor packing a catalyst according to claim 21, wherein the catalyst is acatalyst for producing acrylic acid or methacrylic acid.
 24. The methodfor packing a catalyst according to claim 21, wherein a net mesh of thefunnel is smaller than outer diameters of the catalyst and an inertsubstance.
 25. The method for packing a catalyst according to claim 21,wherein the net of the funnel is provided at an inclined portion of thefunnel and an angle of the inclination is 10 to 75°. 26-30. (canceled)